Antennas are used to receive or radiate electromagnetic energy. Generally, the antenna forms part of a communication system and the electromagnetic energy carries information in the form of a signal on a carrier signal at one or more desired frequencies.
A patch antenna is one type of antenna that gets its name from the fact that is essentially a metal patch disposed over a ground plane. The ground plane and metal patch are separated by a dielectric, which may be air, foam or other suitable dielectric substrate. The electromagnetic energy is received by, or radiated from, the metal patch. A combination of the dielectric constant, size of the patch, size of the ground plane, and spacing between the ground plane and patch determine a resonant frequency for the patch antenna. Patch antennas are popular because they are easy to fabricate using lithographic patterning such as conventional printed circuit board etching and semiconductor processing.
A conventional patch antenna 10 is illustrated in FIGS. 1A and 1B with a top view and a side view, respectively. The patch antenna 10 includes a substrate 14, a ground plane 16, and a patch radiator 12. A feed line 18 couples to the patch radiator. Generally, the feed line 18 connects the patch antenna 10 to an impedance-controlled connector, an impedance-controlled cable, or a combination thereof.
As stated earlier, patch antennas are widely used because they are relatively easy and inexpensive to fabricate. However, patch antennas generally have a relatively narrow bandwidth. Consequently, conventional patch antennas may not be as useful in applications requiring a wider bandwidth. In addition, most patch antennas generally include a connection from the antenna board to another board for receiving a signal from the antenna. These off-board connections to patch antennas can be difficult because the impedance must be carefully matched to the antenna.
In an effort to increase bandwidth, some patch antennas do not use a substrate. Instead, these patch antennas suspend the metal patch in air above the ground plane with spacers. These air-spaced patch antennas can achieve a wider bandwidth. However, because of the spacers, air-spaced patch antennas consume much more space and are often less rugged than substrate-based patch antennas.
There is a need for patch antennas that have increased bandwidth compared with currently available patch antennas. In addition, there is a need for an enhanced connection arrangement for patch antennas. Finally, there is a need for a broadband patch antenna having the favorable size and durability characteristics of a substrate-based antenna.